Evaluation of cytotoxicity and degree of conversion of orthodontic adhesives over different time periods

Abstract

As new orthodontic resin adhesives continue to be marketed, rapid and sensitive tests for examining their toxic effects at the ' cell and tissue level ' are needed because patient safety has been identifi ed as a legal concept. The objective of the present study was to evaluate the cytotoxicity and degree of monomer conversion of orthodontic adhesives over different time periods. Seven adhesives: Transbond ® XT, Transbond ® Color Change, Quick Cure, EagleBond, Orthobond ® , Fill Mágic ® and Biofix ® were evaluated for their cytotoxicity in L929 fibroblastic cells and for their degree of monomer conversion over different time periods. Three control groups were also analysed: Positive control (C+), consisting of Tween 80 cell detergent; Negative control (C-), consisting of PBS; and cell control (CC), consisting of cells exposed to any material. The dye-uptake technique that involves the absorption of a neutral red dye in viable cells was used for the cytotoxicity evaluation and the degree of conversion was evaluated using spectroscopy with infrared. The results showed the cytotoxicity of the adhesives at 24, 48, 72 and 168 hours. At these times, the viability values presented for these materials were statistically different from the groups CC and C-(p < 0.05). At 168 hours, all the groups showed low cytotoxicity with high cell viability and with no statistical difference with the groups CC and C-(P > 0.05). In the monomer conversions there was a percentage increase of monomer conversion from 24 to 72 hours. A direct correlation could be observed between cytotoxicity and monomer conversions. From this work it can be concluded that all adhesives evaluated are cytotoxic at the times of 24, 48 and 72 hours. Monomers continued conversion even after photopolymerization had stopped.

Assessment of the degree of conversion in light-curing orthodontic resins with various viscosities

“…Ferracane and Greener [27] studied unfilled Bis-GMA-based dental resins that had a DC ranging from 55 to 72 %. Data related to the TR system, which showed the lowest DC % value, was similar to the findings of other studies that tested the same resin for cytotoxicity and DC [19,23]. Two resins from Opal Orthodontics, the OF and OS, showed the highest DC % values, but there was no statistical differences among the resins.…”

“…different DC values) [14]. The differences found in conversion values could be attributed to variation in resins composition, in terms of monomeric systems, type and quantity of load particles, concentration of diluents and initiators [19]. The percentage of chemical conversion in the orthodontic resins analyzed decreased within a range of 24.6-53 %, which is in contrast to the range of 55-75 % that was reported in other studies [20][21][22].…”

Evaluation of the cytotoxicity of polyurethane and non-latex orthodontic chain elastics

“…In this study, we used neutral red dye as it is largely employed for identification of L-929 cell viability [23,24]. Dead or damaged cells cannot incorporate vital stain, thus not being recognized on optical reading.…”

In vitro study of cytotoxicity of orthodontic elastomeric ligatures

“…Spectrophotometric essay allows rapid and reliable evidence of cell viability to be obtained based on the use of vital stain incorporated by viable cells [23][24][25][26] . In this study, neutral red dye was used, as it is widely used for identifying L-929 cell viability 23,[25][26] .…”

“…In this study, neutral red dye was used, as it is widely used for identifying L-929 cell viability 23,[25][26] . Dead or damaged cells cannot incorporate vital stain, and are thus not recognized on optical reading.…”